ticket 285: ready to close

rev. 3209 contains changes to optimize.brent (I implemented the brent
class in the way proposed by Alan Isaac + 4 tests related to brent were
added).

So I guess the ticket 285 should be closed.
Also, I have changed some docstrings related to brent and some other
funcs ():

If bracket is two numbers *(a,c)* then they are
   assumed to be a starting interval for a downhill bracket search
   (see bracket);* it doesn't always mean that obtained solution will
satisfy a<=x<=c*.

(As for me some weeks ago I was surprised to obtain solution from
outside of the (a,c) interval, MATLAB has only one func fminbound that
yields solution strictly from the given interval, but some
scipy.optimize line-search routines use strictly the interval and some
other, like brent, use only as starting interval for bracket search, and
this is not properly descriebed in documentation).